There are troops on the ground, these 70,000 or so people that cameron mentions plus the Syrian army. Cutting off the supply of arms from Saudi Arabia and other places; cutting off their supply of funds by not buying their oil; cutting off their propaganda by closing down their websites, cutting off their supply of fighters by closing their borders; continuing unmanned drones targeting their leaders; continuing to support the Iraqi government; providing better humanitarian support to the refiugees so they can return and rebuild their country in time; providing positive support to British mosques and imams to counter the terrorist propoganda; targeting development funding to deprived parts of the UK where homegrown jihadis are being bred.
For me, these are all better uses of the millions that we're otherwise spending on adding our bombs to those of the French, the Syrians, the US, the Russians. It actually gets us thinking about the issues and not just taking the easy route out by saying bombing is the answer.
The Germans bombed Britain for years but it didn't win them the war.
The contention of most of those opposed to bombing is that the 70,000 troops simply do not exist. They are hardly a regular army if they do. The Caliphate has no borders and WE are not buying their oil. Read up on it a bit eh?